Thiopental, a well-known
barbiturate, is often used in patients who are at high risk of developing
cerebral ischemia, especially during brain surgery. Although
barbiturates are known to affect a variety of processes in the cerebral cortex, including oxygen consumption by the mitochondria, the interrelation between mitochondrial function and
anesthetics has not been investigated in detail under in vivo conditions. The aim of this study was to examine the effects of
thiopental on brain functions in normoxia and under partial or complete
ischemia. The use of the multiparametric monitoring system permitted simultaneous measurements of microcirculatory blood flow,
NADH fluorescence, tissue reflectance, and ionic and electrical activities of the cerebral cortex.
Thiopental caused a significant, dose-dependent decrease in blood flow and a significant decrease in extracellular levels of
potassium, with no significant changes in
NADH levels in normoxic and ischemic rats. Following complete
ischemia (death), the increase in the reflectance was significantly smaller in the anesthetized normoxic group versus the awake normoxic group. The time until the secondary increase in reflectance, seen in death, was significantly shorter in the anesthetized ischemic group. In conclusion, it seems that the protective effect of
thiopental occurs only under partial
ischemia and not under complete
ischemia.